“Actual entities – also called actual opportunities – are the ultimate realities of which the world is composed” (PR 18).

As with Democritus’s atoms, they are micro-cosmic entities, whose aggregates, called companies or nexus, are macroscopic entities of our daily experience — trees, houses, people. But while Democritus atoms are an inert, unalterable material substance, Whitehead’s actual entities are “drops of experience, which are complex and interdependent” (PR 18), vital, and transient.

To support that the ultimate realities which the world is composed of, are drops of experience is not to say that consciousness enters the inanimate nature, because conscience can only characterize extremely complex existing entities, and actual entities have the potential of productive complexification of consciousness only when they are members of extremely complex societies such as the one we call the human brain. Whitehead’s intuition is to see that if it’s a unique thing to take seriously the doctrine of evolution and to support that the creatures endowed with sensitivity and intentionality emerge from the primordial magma, then this magma should be understood in such a way that the emergence from it of animals and beings human is intelligible. He defends consequently a neutral monism in which actual entities are not fragments of a material stuff or leibnizian souls, but rather units of process that may be linked to other existing entities to form temporal veins of material, or may be related to other complex actual entities, all entangled in a complex society such as the brain, to form a road of inheritance that we identify with the conscious soul of a person that lasts. (See structured society for more details)

Actual entities are thus units of process and the title Process and reality intends to indicate that these units of microcosmic processes are for Whitehead last realities: “you cannot go behind the current entities to find there some reality which is more important’ (PR 18). On the other hand, to make the mistake of regarding an aggregate of existing entities as a last reality, is to fall into the sophism of badly placed concrete. Descartes has been guilty of this sophism when he characterized the mind and the matter as being two kinds of separate realities.

An actual entity is “the unity to attribute in special case of concrescence” (PR 212). A concrescence is a joint growth of the remains of the decaying past in the vibrant immediacy of a new present unit. An actual entity lasts only a moment – the moment of his becoming, of his

active trial of self-creation from the elements of the past which perish – then it also perishes, and, once thus objectively immortal, becomes a datum dead for successive generations of existing entities. The concrescence of an actual entity begins with a receptive, passive, moment when the given-being of the past is projected onto it; it then completes its fate with a series of creative supplementales phases that adjust, integrate, and perhaps modify the given data. In simple actual entities, there is a simple reiteration of the given: they are ” vehicles designed to receive, store, and restore without gain or loss ” (PR 177). The complex actual entities enjoy a complex succession which is the result of their social involvement, and this complexity of succession creates an originality in the supplementales phases which are the means to complete the integration and unity”.